Biomechanical relation between the region of femoral head becrosis and femoral neck fracture after the total hip resurfacing

Objective:To observe and approach the relation between the region of femoral head necrosis and femoral neck fracture after the total hip resurfacing by biomechanics. Methods:Twenty-five normal adult proximal femur were harvested. They were divided into five groups at random the different regions of femoral head necrosis were and simulated : normal, 10%,20% both in human femoral head's weight bearing region and 10%?20% in non-weight bearing region ,both of them were tested in vitro by simulating single-leg stance phase. Rigidity of the whole proximal femur and the strain value at the juncture of femoral head and neck under 0,500N,1000N load ... were evaluated , until the femoral neck fracture. Results:The intensity and the bearing capacity of femoral neck were found to be smaller in the necrosis of the femoral head's weight bearing region than in the non-weight bearing region. The groups of 10% and 20% all have this tendency. The difference between the two is 17%, and there is a remarkable statistical difference(P0.001). Conclusions: The region of femoral head necrosis influences the bearing capacity and the intensity of femoral neck. If the femoral head necrosis of femoral head's weight bearing region is up to 20%. The hip resurfacing shonld be choosen cautiously, because the femoral neck fracture is easy to occur.